The subject matter disclosed herein relates to a flow control assembly, and more specifically to a flow control assembly having a wall with first and second chambers, where the second chamber directs a fluid path into a vortex configuration.
Generally, a turbine stage of a gas engine turbine includes a row of stationary vanes followed by a row of rotating blades in an annular turbine casing. The flow of fluid through the turbine casing is partially expanded in the stationary vanes and directed toward the rotating blades, and is further expanded to generate power. There is a physical clearance requirement between the tip of the rotating blade and an interior surface of the turbine casing to generally avoid interference between the blade and the turbine casing. Typically, turbine buckets are provided with a cover for improved aerodynamic and mechanical performance. A rail protruding out of the cover is used to reduce the physical clearance between the turbine casing and the rotating blade. The clearance requirement varies based on the dynamic and thermal behaviors of the rotor and the turbine casing.
If the clearance requirement between the turbine casing and the rotating blade is relatively high, then a relatively high amount of high energy fluid flow is able to escape between the tip of the blade and the interior surface of the turbine casing without generating any useful power during turbine operations. The escaping high energy fluid flow constitutes tip clearance loss and can be one of the major sources of losses in the turbine stages. For example, in some cases, the tip clearance losses constitute 20-25% of the total losses in a turbine stage.
Any reduction in the amount of tip clearance flow can result in a direct gain in power and performance of the turbine stage. Typically, such reductions can be achieved by reducing the physical clearance between the rotor tip and the turbine casing. This reduction, however, also increases the chance rubbing or interference between the rotating and stationary components. Another approach to reduce the tip clearance flow involves reducing the effective clearance between the rotor tip and casing by employing a duel vortex chamber in the turbine casing. However, this approach may be difficult to implement due to aerodynamic issues in the turbine.